Known rigid-shell ski boots of this type generally comprise foot-retaining systems arranged within the front part of the boot, corresponding essentially to the metatarsal region of the foot. Such retaining systems are most often operated from outside the rigid shell by means of a two-position lever, one position of which is known as the "unlocked" position, and the other as the "locked" position. Moving from one of these settings to the other produces quick tightening or quick release of the boot. For example, the ski boots described in French Pat. Nos. 2,547,487; 2,468,322; and 2,467,559 show foot-retaining systems of this type comprising, inter alia, an eccentric or cam-equipped lever that acts either on the translational position of a threaded sleeve to which the foot-retaining unit is connected, or, simultaneously, on the translational position of a threaded sleeve connected to a retaining element and on the position of a support shank carrying a nut connected to another foot-retaining element. To adjust the foot-retention setting on such systems, the lever is first shifted into the "unlocked" position, corresponding to a quick release by rotation of the cam, following which it can be screwed in one direction of the other, causing the threaded sleeve to move and thereby adjusting the foot-retaining element connected to said sleeve.
In the constructional examples described above, the cam-equipped or eccentric levers, when in "locked" position, expose a relatively large space together with the recesses in which they are housed on the rigid shell. This space, which corresponds to the travel of the cam, is aesthetically unappealing but cannot be reduced without producing a corresponding reduction in the length of travel of the cam. This, however, is undesirable, since it is the travel of the cam that determines the range of the quick-release means.